cryptoeasy

Sub

spbctf

Task: Decrypt ciphertext that appears to use substitution cipher. Solution: Identified it as a block permutation cipher (not substitution), recovered the permutation using known flag prefix spbctf{, and decrypted all 8-character blocks.

$ ls tags/ techniques/
known_plaintextblock_cipherpermutation_cipherclassic_cipher
known_plaintext_attackblock_permutation_recovery
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